The primary goal of the proposed research is to understand the molecular genetic basis for the development of B-cell leukemias and lymphomas. Murine leukemia retroviruses (MuLVs) cause leukemia and lymphoma in susceptible strains of mice by insertional mutation of cellular proto-oncogenes or tumor suppressor genes. Some AKXD recombinant inbred strains of mice have a high incidence of B-cell lymphomas caused by MuLV insertion, making them valuable resources for identifying new proto-oncogenes using the retrovirus as a molecular tag. Viral insertion site amplification (VISA) can quickly identify proviral flanking sequences in the AKXD somatic tumors by obtaining a viral sequence tag (VST). An analysis of four AKXD strains 35 genes well as many unknown VSTs altered by retroviral insertion. We will extend this study to obtain VSTs for the remaining five AKXD strains that develop primarily B-cell lymphomas. Insertions at one locus called lymphoid viral insertion site 1 (Lvisl) account for 23 percent of the proviral insertion mutations in the AKXID B-lineage tumors, suggesting that genes at Lvis1 play a primary role in the development of hematopoietic disease. Two genes proximal to Lvisl are misexpressed: the hematopoietic homeobox gene, Hex, and a kinesin-related spindle protein, Eg5. Either of these genes could play a role in leukemogenesis, and we will examine this hypothesis by 1) overexpressing the genes in transgenic mice, and 2) transducing the genes into hematopoietic cells using retroviral gene transfer. These genes may act singly or together to potentiate leukemogenesis. Further, we propose to examine the role of Hex in hematopoeisis by eliminating function by a tissue-specific targeted gene disruption. The VSTs represent the majority of genes that contribute to disease onset and progression within the hematopoietic lineages of the AKXD strains. To make the data publicly accessible, we will develop a database describing VSTs and tumor phenotypes. Through collaborations, we will examine the potential involvement of some genes in human leukemias and lymphomas. These data can be integrated with both genomic and gene expression profiles from human cancers to uncover the pathways involved in the development of leukemia and lymphoma in both mouse and human.